The gene has been defined by the Danish botanist, plant physiologist, and geneticist Wilhelm Ludvig Johannsen, in 1909 in the book Arvelighedslærens Elementer (elements of the study of heredity), as the unit of heredity.

The US supreme court has ruled unanimously that natural human genes cannot be patented, a decision that scientists and civil rights campaigners said removed a major barrier to patient care and medical innovation.

In the simplest case and in principle, a gene locus is supposed to be the physical reality corresponding to the theoretical gene unit of heredity; in practice, things are far more complicated and confused, which is well known and acknowledged. However, these questions are the subject of still very active scientific research, as well as the topic of both scientific and philosophical questions, especially on the real compatibility between both senses of the term.